feat: add supports for generics constraints

[converter][web]

#107

Author: MangelMaxime

src/Glutinum.Converter/Printer.fs

@@ -174,7 +174,7 @@ let private printAttributes
         printer.NewLine
     )
 
-let private tryTransformTypeParametersToText
+let rec private tryTransformTypeParametersToText
     (typeParameters: FSharpTypeParameter list)
     =
     let printer = new Printer()
@@ -187,8 +187,23 @@ let private tryTransformTypeParametersToText
             if index <> 0 then
                 printer.WriteInline(", ")
 
-            printer.WriteInline("'")
-            printer.WriteInline(typeParameter.Name)
+            printer.WriteInline($"'{typeParameter.Name}")
+        )
+
+        typeParameters
+        |> List.filter _.Constraint.IsSome
+        |> List.iteri (fun index typeParameter ->
+            match typeParameter.Constraint with
+            | Some constraint_ ->
+                if index = 0 then
+                    printer.WriteInline(" when ")
+                else
+                    printer.WriteInline(" and ")
+
+                printer.WriteInline($"'{typeParameter.Name}")
+                printer.WriteInline(" :> ")
+                printer.WriteInline(printType constraint_)
+            | None -> ()
         )
 
         printer.WriteInline(">")
@@ -198,15 +213,15 @@ let private tryTransformTypeParametersToText
     else
         None
 
-let private printTypeParameters
+and printTypeParameters
     (printer: Printer)
     (typeParameters: FSharpTypeParameter list)
     =
     match tryTransformTypeParametersToText typeParameters with
     | Some typeParameters -> printer.WriteInline(typeParameters)
     | None -> ()
 
-let rec private printType (fsharpType: FSharpType) =
+and printType (fsharpType: FSharpType) =
     match fsharpType with
     | FSharpType.Object -> "obj"
     | FSharpType.Mapped info ->

src/Glutinum.Converter/Reader/TypeParameters.fs

@@ -3,7 +3,6 @@ module Glutinum.Converter.Reader.TypeParameters
 open Glutinum.Converter.GlueAST
 open Glutinum.Converter.Reader.Types
 open TypeScript
-open Fable.Core.JsInterop
 
 let readTypeParameters
     (reader: ITypeScriptReader)
@@ -18,7 +17,9 @@ let readTypeParameters
         |> List.map (fun typeParameter ->
             {
                 Name = typeParameter.name.getText ()
-                Constraint = None
+                Constraint =
+                    typeParameter.``constraint``
+                    |> Option.map reader.ReadTypeNode
                 Default = None
             }
         )

tests/specs/references/typeAlias/constraints/multiple.d.ts

@@ -0,0 +1,3 @@
+export class Foo<A> { }
+
+type ReturnType<A, T extends Foo<A>, B extends Foo<A>> = [A, T, B]

tests/specs/references/typeAlias/constraints/multiple.fsx

@@ -0,0 +1,23 @@
+module rec Glutinum
+
+open Fable.Core
+open Fable.Core.JsInterop
+open System
+
+[<AbstractClass>]
+[<Erase>]
+type Exports =
+    [<Import("Foo", "REPLACE_ME_WITH_MODULE_NAME"); EmitConstructor>]
+    static member Foo<'A> () : Foo<'A> = nativeOnly
+
+[<AllowNullLiteral>]
+[<Interface>]
+type Foo<'A> =
+    interface end
+
+type ReturnType<'A, 'T, 'B when 'T :> Foo<'A> and 'B :> Foo<'A>> =
+    'A * 'T * 'B
+
+(***)
+#r "nuget: Fable.Core"
+(***)

tests/specs/references/typeAlias/constraints/single.d.ts

@@ -0,0 +1,3 @@
+export class Foo<A> { }
+
+type ReturnType<A, T extends Foo<A>> = T

tests/specs/references/typeAlias/constraints/single.fsx

@@ -0,0 +1,23 @@
+module rec Glutinum
+
+open Fable.Core
+open Fable.Core.JsInterop
+open System
+
+[<AbstractClass>]
+[<Erase>]
+type Exports =
+    [<Import("Foo", "REPLACE_ME_WITH_MODULE_NAME"); EmitConstructor>]
+    static member Foo<'A> () : Foo<'A> = nativeOnly
+
+[<AllowNullLiteral>]
+[<Interface>]
+type Foo<'A> =
+    interface end
+
+type ReturnType<'A, 'T when 'T :> Foo<'A>> =
+    'T
+
+(***)
+#r "nuget: Fable.Core"
+(***)